"以大钉钉牢" can be translated as "to fasten securely with large nails" or more naturally as "to nail down firmly (with big nails)" depending on the context.
For example:
We need to nail down the boards firmly with large nails to ensure they don't come loose. （我们需要用大钉子把木板钉牢，以确保它们不会松动。）